Sensitized photographic element and process of making the same



Patented Mar. 18, 1941 UNITED STATES PATENT i SENSITIZED PHOTOGRAPH)ELEMENT AND 4 j PROCESS OF MAKING THE SAME I Kerk. N. Y.

I No Drawing.

I plication October 14, 1937,

I Serial No. 168,902 7 cam.. (on. 95-7) graphic elementsincorporatingcolor formers, by

10 virtue of the inability of properly associating or bonding suchcolorformers with the silver. halide Particles.

Generally, two methods have :been known, the first being that whereincolor-forming compound is dispersed among the silver halide grainscarried in an emulsion, whereby the color former essentially permeatesthe emulsion, and in hitor-miss fashion becomes associated, through surface contact, with the silver halide particles; and

the other in which light sensitive substances are formed byprecipitating silver halides in the presence of color formers as, forexample, generally by reacting a soluble halide, a soluble silver salt,and a color former, in a colloid forming the 2 emulsion.

With respect to the first of these methods, little need be furtherstated, in view of its obvious deficiencies; with respect to the second,several factors limit the degree and amount of association of the colorformer to the silver halide, to such extent as to minimize theefiectiveness of this procedure for application in recording colorimages. Primarily, the restrictions result through the following: first,the color former being normally soluble in small quantities only, in thesolution incorporating the soluble halides and silver salts of particlemass concentration far greater than that of the color former, with theresult that the chemically formed insoluble silver halide crystal orgrain must often form and ripen without any contact or collisions withthe discrete color former particles in the reacting mixture; secondly,an aqueous medium in large quantities being required as the solventinthe colloid in which the reaction is carried out and the color formerof necessity being insoluble in such medium, the amount of physicalassociation or afliliation of the discrete color former particles to andwith the silver halide crystal nuclei as chemically formed is at. bestsmall, since such afiiliation involves the physical intercombination of.discrete particles of two'different precipitates having no directrelationship other than being present in the solvent; lastly, thereaction involv- V ing thesoluble halide, solublesilver salt and theinsoluble color former, being one wherein the' halide and the silversalts are first intended to react chemicailyto form. a silver halideprecipitate, and thereafter the precipitated silver halide and discretecolor former particles are intended 6 to unite physically, and the colorformerdiscrete particles being essentially'and at all times during thechemical reaction aforesaid an insoluble precipitate, the amount ofaffiliation, surface in this case, is necessarily restricted and farfrom 10 the mass or molecular association necessary for the purpose,since no direct interaction of the radicals of the reagents, forming thesilver halide crystals-is had with thecolor former, to place the colorformer particles and silver halide crys- 15 tals in the requiredproximity. Broadly, it is an object of this invention for the productionof light sensitive halides incorporating color formers, by providing anoptimum condition for inter-association of the light sensi-" tivehalides and the color formers, through the reaction of media providingfor a simultaneous chemical intercombination of radicles forming thesilver halide and physical adsorption and, occlusion of the particleofthe color former, 25 both chemical and physical reactions beingconsummated at the same situs.

Further it is an object of this invention toprovide for the formation ofthe light sensitive element of a photographic emulsion, wherein 0 colorformers are associated with the silver halide, by reacting the silvercompound of a color former with a soluble halide and forming, bypresenting the color former in situ with the resulting silver halidecrystals in a simultaneous 35 chemical and physical reaction, amicro-homogeneous and micro-heterogeneous complex in the nature of asilver halide crystal incorporating the color former radical orparticle, such color former simultaneously at the completion of the 40chemical reaction and subsequent ripening steps :being adsorbed andsubstantially occluded into the light sensitive silver halide crystalnucleus as it is formed and grows.

Specifically, it is an object of this invention'to 45 form as a lightsensitive silver halide, a reaction product of a silver salt of a colorformer and a soluble halide in substantially molecular proportions,whereby there is formed during and by such reaction, a silver halidecrystal to which there is adsorbed and in which there is occluded thecolor former particle or radical, from the silver salt of which colorformer the silver radical of the formed insoluble halide'has separated.

In general, the invention comprises a positive 55 and'efi'ective methodof accomplishing the union v or bonding of a color former with a silverhalide to provide a light sensitive element color recordan exchange ofradicals is introduced and simultaneously therewith a physical reactioneflfectuated at the situs ofand during-the course of formation of thesilver halide associating firmly by adsorption-and occlusion the colorformer radical or particle with the silver halide crystal nucleusproduced by the chemical reaction as it ripens.

These and other advantages, capabilities and features of the inventionwill appear from the subjoined detailed description of one specificembodiment thereof. a

In accordance with this invention the photographic element may be eitherof a single emulsion or a series of emulsions in which the silver halideand color former are united or bonded in a manner that the color formeris adsorbed or occluded in the silver halide crystal, being transparentand relatively colorless, the color effect desired for recordingparticular color values being established after exposure by and indevelopment.

In carrying out the invention the color sensitive emulsionsfor therespective different colors are prepared as follows:

A silver salt of a color former having very slight solubility in aqueoussolution is, together with an equal molecular amount of potassiumbromide, disposed in a colloid serving as a carrier as, for example,gelatin, agar agar, or cellulose derivatives, there being present in thereacting mixture a small'quantity of acid. The reaction involved is thechemical combination of the silver radical from the color former saltand the bromine radical of the halide to form the insoluble lightsensitive halide, the alkali oi the halide being combined with thenegative radical of the acid, and the hydrogen radical of the acid beingunited to the color formepin replacement of the silver radical of thesilver color former salt. The insoluble silver halide formed by thechemical reaction in the form of nuclei are physically bonded to thecolor former from which the silver has beenchemically separated, withthe color former' being adsorbed and occluded to the respective silverhalide nuclei as they ripen, due to the physical proximity of the colorformer molecules, to the latter as they are formed, with the result thatthe light sensitive element being in the nature of a complex silverhalide-color former, is dispersed in the colloid, as the latter jellsupon removal of the solvent.

, Since it is desired to form different color sensitive emulsions,silver salts of various color formers may be applied to establish therespective color values capable of production by exposure anddevelopment and following are examples of i the same.

To produce an emulsion for the red color, a

' silver nitrophenyl acetonitrile is reacted with potassium bromide anda dilute acid such as nitric acid, the reaction being as follows:

Where the dotted line in the formula on the right hand side of theequation, between the nitro phenyl aceto nitrile and the Ag bromide,indicates the close association of the respective molecules.

To produce an emulsion tor the blue color silver pentabrom alphanaphthoi is reactedwith potassium bromide and nitric acid in accordancewith the following reaction:

Br Br v Br he Br r AgBr To produce an' emulsion for the yellow color,

silver aceto-acet-2,- 4 dichloranilide is-reacted with potassium bromideand dilute nitric acid in accordance with the following reaction:

cmcocmconOm Ag+BrH Agllr Furthermore, it is not necessary for thereacting substances to be present in molecular proportions. For example,it may be desired for given purposes to produce an emulsion containingPa complex light sensitive medium and consisting of adsorbed andoccluded silver halidecolor former-silver salt of color former; Thus, 2parts of the silver salt of the color former may be used with 1 parteach of potassium bromide and nitric acid, or 2 parts of the silver saltof the color former and one part of the acid halide.

Cl Cl CIIa.CO,CH2.CO.N (.I CHz.CO.CHz.CO.N Cl ,0

Ag s

+BrH 5 IM; ngBr '01 omcocmcoxQm 1 C cmcocmcogQm These silver halide andcolor formers complexes which provide'fonthe production of definitecolors on exposure and development may be sensitized for specificregions of the spectrum in the ways well'known in the art.

Thus, the emulsion for red may be opticallyv sensitized for green bytreatment, during or after the production of the emulsion, with anappropriate green sensitizing dye as erythrosine; The emulsion for bluemay be optically sensitized for red by treatment with an appropriate redsensitizing dye as pinacyanol; the emulsion for yellow being nativelysensitive for blue and thus need not be especially treated.

By thus mixing emulsions for each of the three colors,'which have beenappropriately sensitized, a mixed emulsion is produced which may becoated as a single layer on a carrier, forming a photographic lightsensitive element for the production of the three colors. The singleemulsion alternately may be coated in three layers one upon another, ona carrier, thus producing the more familiar element for three colors.

After exposure the emulsions are treated with or Farmers reducer.

' the color former and the silver halide are sub- These color images aresuperior to those produced by other processes by virtue of the factthat'the color former is constantly in contact with the silver halidecrystal at its formation and during its period of ripening and growthand the ratio of mass particles of respectively s'tantially molecular;the color former. at the instant of liberation and the instant offormation of the nucleus of silver halide being present in molecularlydispersed form at the crystal face of the halide for simultaneousadsorption and occlusion as the silver halide nucleus grows throughripening. It is to be understood in this process that with the ionicexchange of radicals there are produced two insoluble substances at onesitus, and since one of the insolubles, the silver halide, is of anature once its nucleus has formed as to enlarge its crystal form onripening in a duration of time; and since the color former particles areabsorbableand are at thesitus of the formation of the silver halidenucleus, the physical phase of the interaction between the respectivesilver halide and color former commences immediately and 'is carried onprogressively with the resultant effect, that there is no difier'entialseparation of the particles but rabheran agglomeration, that is, abuilding up of the particles of one precipitate by absorbing theimmediately available particles of the other.

Wherever in the specification the words color former have been used, itis to be understood that the expression refers to a color forming silverhalide crystal having adsorbed and occluded thereon a color formingdevelopment component through chemical and physical interaction, whichconsists in reacting in solution a pre-formed silver salt of a colorforming development component with a soluble halide.

2. A-method of making a light sensitive complex for photographicpurposes, incorporating a silver halide crystal having adsorbed andeluded thereon a color forming development componentthrough chemical andphysical interaction, which consists in reacting in solution andinrmolecular proportions a pro-formed silver salt ofa color formingdevelopment component with a soluble halide.

3. The methodof making a light sensitive photographic element, whichconsists in precipitating in a colloid medium, a silver halide-colorforming development component complex through reaction of a pre-formedsilver salt of a color forming development component with a solublehalidein acid solution.

4. The method of making a light sensitive photographic element, whichconsists in forming at one and the same situs by chemical and physicalunion, a complex incorporating a silver halide having adsorbed andoccluded thereon an organic color forming development component byreacting in" solution the pre-formed silver salt (if a color formingdevelopment component with a soluble halide in-a colloidal mediumserving as a carrier.

5. In the preparation of a light sensitive photographic medium,.theprocess which comprises reacting in solutiona pro-formed soluble halidewith a silver salt of a color forming development component in acolloidal medium serving as a carrier, to form at one and the same situsthrough precipitation and ripenin a complex salt in the nature of asilver halide crystal having a color forming development componentadsorbed and occluded thereto.

6. In the preparation of a light sensitive prises reacting insolution-in molecular proportions within a colloidal medium serving as acarrier, a soluble halide and apre-formed silver salt of a color formingdevelopment component for precipitating out and forming by subsequentripening, a complex salt incorporating a silver halide crystal havingthe color forming development component bound thereto by adsorption andocclusion in substantially molecular proportions.

7. In the preparation of a light sensitive photographic medium, theprocess which comprises reacting in solution in acolloidal mediumserving as a carrier a soluble halide and a preformed silver salt of acolor forming development component for producing at the same situs bysimultaneous chemical and physical interaction, a macro-homogeneous andmicroheterogeneous complex in the nature of asilver' halide crystalincorporating a color forming development component.

' MAC GOODMAN.

